Add support for CodeSpaces

[mattvv]

This adds a devcontainer that has elixir pre-installed so you can do the koans without having to install elixir. Selfishly useful for doing some koans while I'm playing games on my windows PC :)

To use this, you can simply clone the repo using codespaces and the terminal will automatically appear and you can get started by doing

mix deps.get

and then

mix meditate

[Nezteb]

@iamvery Works on my machine! (well, GitHub's machine but you get the idea 😂)

[iamvery]

@Nezteb thank you for confirming. @ukutaht @felipesere either of you have thoughts?

[ukutaht]

Strongly in favour. For people starting out with Elixir this is probably the best way.

Before merging, does CodeSpaces have a convenient way to launch it with a link? Would be nice to promote this with a Run in CodeSpaces button in the README. Otherwise, maybe add instructions on how to use this in the README?

[Nezteb]

@ukutaht There is a way in the GitHub UI to do this relatively easily: https://docs.github.com/en/codespaces/developing-in-codespaces/creating-a-codespace#creating-a-codespace

Aside from that there is also the github.dev editor (which can be accessed by pressing the period key . on your keyboard when on a repo's page). https://docs.github.com/en/enterprise-cloud@latest/codespaces/the-githubdev-web-based-editor#opening-the-web-based-editor

As far as I can tell there is no easy way to create a Codespaces link that auto-creates one for people (similar to how Codesandbox does it).

[CompuIves]

Swooping in! (I heard CodeSandbox 😂)

In the future, CodeSandbox should be able to run Elixir as well. At CodeSandbox we're currently experimenting with this (our backend is in Elixir/Phoenix), by allowing you to configure the Elixir version in CodeSandbox Projects.

Not much to add, just wanted to say that we might support Elixir in the future! 😄

[Nezteb]

(our backend is in Elixir/Phoenix)

[iamvery]

What's the status on this?